I have two different Ryet carbon saddles on my two 268 frames. On one of the saddle the rails measure 9 mm high, on the other 11 mm.
I was asked by Velobuild if I needed a special clamp for carbon rails and was send two sets. They fit fine on the one with 7x9 mm (picture 1) but terrible on the one with 11 mm (picture 2). I just don't think that the side clamping mechanism in general is great on these kind of carbon rails. Should have done my research better before I ordered the Ryet knock off of the Pro Stealth II.
I'm on the look out for a clamp that goes closer to 11 mm than the one I've got.

-7x9 saddle clamp for carbon rails. On my particular clamp when using my AliExpress carbon saddle (7x9 rails), visually it does not appear as if the clamps are fully engaging with the rails. Other 268 owners with carbon saddles have not experienced this, and so far the saddle has stayed put. However, the saddle clamp bolt is now slightly bent from trying secure to the rails. Also a non-issue if you're using 7x7 rails as VB also supplies clamps for that too. Just something to be aware of.

I also encountered the issue with the 7x9 saddle clamp. I reached out to Velobuild and they sent me a new one. I have not received it yet but I'll comment once I have it.

Just did my first ride with the 268, and it feels great.